Understanding Tree Nut Allergies

Tree nuts are an important food source worldwide as well as one of the most common food allergies. Approximately one in 20 Americans is allergic to tree nuts. There are a number of different types of tree nuts, and the allergic cross-reactivity between them is high.

However, just because you are allergic to one tree nut does not mean you won't be able to eat another tree nut. The risk varies from person to person.

Symptoms of tree nut allergies are the same as other food allergies, although they tend to be more severe. If allergic to tree nuts, your healthcare provider will advise you to avoid all tree nuts as part of your treatment plan.

Should you eat a tree nut and have an allergic reaction, you may need to use injectable epinephrine and/or an oral antihistamine. Unlike other common food allergies, you are less likely to outgrow a tree nut allergy, especially if you are prone to reactions.

Common Allergies

The risk of allergy to tree nuts varies by the type. Though you can ultimately be allergic to any type of tree nut, there are four that are known to trigger symptoms more than others.

Pistachios

Pistachios commonly cause food allergy symptoms and are cross-reactive to cashews and mangoes. Hay fever to the pollen from the Parietaria weed found in Europe appears to predispose to pistachio allergy.

Almonds

Almonds are the most popular tree nut consumed in the United States and the third most common tree nut allergy. Almonds are commonly used when processing food and are ingredients in breakfast cereals, granola bars, and baked goods. Having an almond allergy may predispose you to other tree nut allergies, especially pistachio nuts.

Cashews

Cashews are the second most common allergy-causing tree nuts. The oil found in the nutshell of the cashew is known to cause contact dermatitis and is related to the oils found in the leaves of poison oak and in the skin of mangoes.

Cashew allergens are similar to those in pistachios, hazelnuts, walnuts, peanuts, sesame, and buckwheat. If you have a cashew allergy, you may also experience allergic reactions to these other foods.

Walnuts

Walnuts, especially English walnuts, are the most common type of tree nut allergy. If you are allergic to walnut pollen, you may experience symptoms of allergic rhinitis. Pecans and walnuts are closely related, so some people who are allergic to one are also allergic to the other.

Less Common Allergies

Other tree nuts may cause allergic symptoms, but sometimes they aren't "true" allergies. Oral allergy syndrome (OAS) occurs when a certain food allergen is similar to an allergen found in tree or grass pollen. As such, they echo the true allergy but tend to be less severe.

Pecans

Pecans are a common food in the southern United States, but less common elsewhere in the world. Approximately one in 20 adults in the U.S. will have a reaction to pecans. If you have a pecan allergy, you may have a walnut allergy as well, given how similar allergens in the two nuts are.

Chestnuts

If you have a latex allergy or an avocado allergy, you may also have a chestnut allergy given the similarity between the allergens found in latex and these foods. Mugwort pollen, apples, and peaches may give you a reaction as well if you are sensitive to chestnuts.

Hazelnuts

Allergy to hazelnut is more common in Europe than in the United States. Hazelnut pollen is a common cause of seasonal hay fever. If you have a hazelnut pollen allergy, you are also at risk for a food allergy to the tree nut itself.

If you have a birch pollen allergy, you may experience oral allergy symptoms with eating hazelnuts. If you have a hazelnut allergy, you may also be allergic to coconut, cashews, peanuts, and soybeans, given the similarity between the allergens in these foods.

Uncommon Allergies

Some tree nuts are less commonly associated with allergy, often because they are not commonly or widely consumed within a population.

Brazil Nuts

Brazil nut allergies are not common, which may be due to their lack of popularity in the U.S. Brazil nut allergies may increase in the future since genetically modified soybeans have proteins similar to those found in Brazil nut allergen. If you are allergic to Brazil nuts, you may also be allergic to walnuts.

Pine Nuts

Pine nuts are a common food in southern Europe, but less common in other parts of the world. They are actually a seed, not a nut, but allergy to pine nuts is possible.

Macadamia Nuts

Macadamia nuts are common in Hawaii and the tropics. There is some cross-reactivity between the allergens in macadamia nuts and hazelnuts.

Coconut

Coconut allergies are rare ​and coconuts are only distantly related to other tree nuts. However, some research shows a similarity between coconut allergens and those in almonds and macadamia nuts.